In the context of Holistic Quantum Relativity's Socratic Dialogue on ATCA and IntentBlog it is useful to note that the Nobel Laureates Prof Albert Einstein (1921) and Sir Rabindranath Tagore (1913) met at Einstein's residence in Berlin, Germany, on 14th July 1930, as photographed. The recorded conversation elegantly demonstrates how the two utilised the language of music, as a metaphor, to forge common ground between science & spirituality.

TAGORE: I was discussing with Dr Mendel [mutual friend] today the new mathematical discoveries which tell us that in the realm of infinitesimal atoms chance has its play; the drama of existence is not absolutely predestined in character.

EINSTEIN: The facts that make science tend toward this view do not say good-bye to causality.

TAGORE: Maybe not, yet it appears that the idea of causality is not in the elements, but that some other force builds up with them an organised universe.

EINSTEIN: One tries to understand in the higher plane how the order is. The order is there, where the big elements combine and guide existence, but in the minute elements this order is not perceptible.

TAGORE: Thus duality is in the depths of existence, the contradiction of free impulse and the directive will which works upon it and evolves an orderly scheme of things.

EINSTEIN: Modern physics would not say they are contradictory. Clouds look as one from a distance, but if you see them nearby, they show themselves as disorderly drops of water.

TAGORE: I find a parallel in human psychology. Our passions and desires are unruly, but our character subdues these elements into a harmonious whole. Does something similar to this happen in the physical world? Are the elements rebellious, dynamic with individual impulse? And is there a principle in the physical world which dominates them and puts them into an orderly organisation?

EINSTEIN: Even the elements are not without statistical order; elements of radium will always maintain their specific order, now and ever onward, just as they have done all along. There is, then, a statistical order in the elements.

TAGORE: Otherwise, the drama of existence would be too desultory. It is the constant harmony of chance and determination which makes it eternally new and living.

EINSTEIN: I believe that whatever we do or live for has its causality; it is good, however, that we cannot see through to it.

TAGORE: There is in human affairs an element of elasticity also, some freedom within a small range which is for the expression of our personality. It is like the musical system in India, which is not so rigidly fixed as western music. Our composers give a certain definite outline, a system of melody and rhythmic arrangement, and within a certain limit the player can improvise upon it. He must be one with the law of that particular melody, and then he can give spontaneous expression to his musical feeling within the prescribed regulation. We praise the composer for his genius in creating a foundation along with a superstructure of melodies, but we expect from the player his own skill in the creation of variations of melodic flourish and ornamentation. In creation we follow the central law of existence, but if we do not cut ourselves adrift from it, we can have sufficient freedom within the limits of our personality for the fullest self-expression.

EINSTEIN: That is possible only when there is a strong artistic tradition in music to guide the people's mind. In Europe, music has come too far away from popular art and popular feeling and has become something like a secret art with conventions and traditions of its own.

TAGORE: You have to be absolutely obedient to this too complicated music. In India, the measure of a singer's freedom is in his own creative personality. He can sing the composer's song as his own, if he has the power creatively to assert himself in his interpretation of the general law of the melody which he is given to interpret.

EINSTEIN: It requires a very high standard of art to realize fully the great idea in the original music, so that one can make variations upon it. In our country, the variations are often prescribed.

TAGORE: If in our conduct we can follow the law of goodness, we can have real liberty of self-expression. The principle of conduct is there, but the character which makes it true and individual is our own creation. In our music there is a duality of freedom and prescribed order.

EINSTEIN: Are the words of a song also free? I mean to say, is the singer at liberty to add his own words to the song which he is singing?

TAGORE: Yes. In Bengal we have a kind of song-kirtan, we call it -- which gives freedom to the singer to introduce parenthetical comments, phrases not in the original song. This occasions great enthusiasm, since the audience is constantly thrilled by some beautiful, spontaneous sentiment added by the singer.

EINSTEIN: Is the metrical form quite severe?

TAGORE: Yes, quite. You cannot exceed the limits of versification; the singer in all his variations must keep the rhythm and the time, which is fixed. In European music you have a comparative liberty with time, but not with melody.

EINSTEIN: Can the Indian music be sung without words? Can one understand a song without words?

TAGORE: Yes, we have songs with unmeaning words, sounds which just help to act as carriers of the notes. In North India, music is an independent art, not the interpretation of words and thoughts, as in Bengal. The music is very intricate and subtle and is a complete world of melody by itself.

EINSTEIN: Is it not polyphonic?

TAGORE: Instruments are used, not for harmony, but for keeping time and adding to the volume and depth. Has melody suffered in your music by the imposition of harmony?

EINSTEIN: Sometimes it does suffer very much. Sometimes the harmony swallows up the melody altogether.

TAGORE: Melody and harmony are like lines and colours in pictures. A simple linear picture may be completely beautiful; the introduction of colour may make it vague and insignificant. Yet colour may, by combination with lines, create great pictures, so long as it does not smother and destroy their value.

EINSTEIN: It is a beautiful comparison; line is also much older than colour. It seems that your melody is much richer in structure than ours. Japanese music also seems to be so.

TAGORE: It is difficult to analyze the effect of eastern and western music on our minds. I am deeply moved by the western music; I feel that it is great, that it is vast in its structure and grand in its composition. Our own music touches me more deeply by its fundamental lyrical appeal. European music is epic in character; it has a broad background and is Gothic in its structure.

EINSTEIN: This is a question we Europeans cannot properly answer, we are so used to our own music. We want to know whether our own music is a conventional or a fundamental human feeling, whether to feel consonance and dissonance is natural, or a convention which we accept.

EINSTEIN: It would be interesting to study the effects of European music on an Indian who had never heard it when he was young.

TAGORE: Once I asked an English musician to analyze for me some classical music, and explain to me what elements make for the beauty of the piece.

EINSTEIN: The difficulty is that the really good music, whether of the East or of the West, cannot be analyzed.

TAGORE: Yes, and what deeply affects the hearer is beyond himself.

EINSTEIN: The same uncertainty will always be there about everything fundamental in our experience, in our reaction to art, whether in Europe or in Asia. Even the red flower I see before me on your table may not be the same to you and me.

TAGORE: And yet there is always going on the process of reconciliation between them, the individual taste conforming to the universal standard.

A white dwarf is a dwarf star and the 'white' that was added to its name was just because, the few dwarfs that were found during their discovery appeared white--I'm not kidding, that's true.

Do you know how dense a typical white dwarf can get?

Well, if you don't, I can answer it for you: they appears in the size of our earth containing almost the entire mass of our sun. That's too much right?

Because of their smaller size and heavier mass these stars are extremely denser and compact objects having the average density approaching 1,000,000 times that of water.

To help you understand the way in which a normal star turns in to a compact white dwarf, let me explain to you the typical life cycle of a typical star.

A star takes birth when large amounts of near by gaseous particles--hydrogen atoms--attracted towards each other through the gravitational force, gets collided and coalesce--after much needed collisions--with each other to produce large quantities of heat along with some heavier compounds. The heat that got released during this process is much like a controlled hydrogen explosion, and is in fact responsible for the star to shine so brightly up in the space.

This heat got one more responsibility to look after: helping the star by restricting the sudden catastrophic gravitational collapse and thus maintaining a slow contraction process . Eventually there comes a stage where the star attains a perfect balance between the gravitational force, that which tries to contract the star even further, and the force that was caused by the heat energy, that which tries to explode the star out. And thus the star remains stable until one of its forces gets weaker, and we all know that it can't be the eternal gravitational force that gets weaker. The contraction process starts again and now the star reaches a stage where it was left with no fuel to burn anymore.

Now, what you think is gonna help the star from the catastrophic gravitational collapse??--earlier it was stopped by the heat energy.

Well, its the outward pressure that was generated due to the repulsions between the sub atomic particles--electrons or neutrons or protons.

Here, the star that which attained balance through the repulsions between electrons is our required 'White dwarf' and the one that was supported by neutron repulsions is named as a 'Neutron star'

Now, if you still got a doubt like: what's gonna happen to our star if the repulsions that were supposed to stop the gravitational collapse can't equal the massive gravitational force?

Yeah, that's a good doubt and it was first occurred to Subrahmanyan Chandrasekhar, a well known physicist, and I'm gonna explain that in my next post.

And please do comment here if you got anything to say..thanks :)Read more...

As I said before a Nova is a completely different process compared with a Supernova. A Nova is actually a sudden brightness that spreads across the surface of a White dwarf--kind of a star. The brightness is the result of a fusion reaction that happens on the surface of the White dwarf, and that fusion reaction is initiated by the matter that was gravitated towards and got accumulated across the surface of the White dwarf from a nearby binary neighbor.

This doesn't cause any sort of huge impact on the White dwarf's dimensions or properties, and hence can happen again and again as long as its neighbor stays close enough, and the matter gets accumulated on its surface.Supernova on the other hand is a complete destruction of a star that which can't able to withstand its own gravity, when it happens to reach a certain mass at the end of its fuel consumption. The limit being found as 1.4 solar masses by Chandrashekar and was popular as Chandrashekar Limit.

Obviously it happens just once for a star that supposedly reaches above or equals Chandrashekar Limit, after burning away its complete fuel, unlike Nova.

Supernova got classified in to two types depending up on the way it reaches the Chandrashekar Limit.

The first one, as I mentioned earlier happens when a star can't burn anymore and endup above or across Chandrashekar Limit. This is more natural as it seems.

-- I will try to give a much detailed explanation in my next post. :)

The second one happens for a White dwarf, where its resultant mass reaches the 'Limit' through accretion of mass from its nearby binary neighbor. It might look like Nova in the beginning but is more powerful and more devastating, as there will be no star left over--other than some Supernova Remnant--at the end of the process that lasts ranging from several weeks to months.

Earlier it was thought that the Supernova is a kind of bigger and brighter Nova and hence the name. And now, the name stayed but not the definition. A Supernova is in noway related to Nova where the former is caused by the gravitational collapse and the later by the fusion reaction.The only thing that appears common for the both at times is White dwarf.Read more...

There was a star somewhere around the sky staying almost unnoticeable, and got burst out suddenly in to a blistering brightness; it's just a one more Supernova!--if not Nova.

The energy and light that was radiated in to the sky during the star's sudden outburst is so heavy that it can easily outshines the entire galaxy--for several weeks to several months depending on the star's mass-- where it resides in, and that happens every time. The energy that got released during the process equals the entire energy that our sun can generate in its entire lifetime.The star explodes and expels the material it was hiding till then, in to the surrounding Interstellar medium at a velocity of up to 30,000 km/s(10% that of light's). The material thus got released expands taking the help of a Shock wave that was generated during the sudden explosion, in the form of gas and dust called a Supernova remnant.

Supernova happens very rare compared with Nova, which is a completely different process and happens very often. For a galaxy in the size of our Milky way, supernova happens just once in every 50 years. Anyways, it's a lot more common process and happens once in every sec, when we look through the entire universe(as the universe breeds stars every sec and they are not eternal).

It's not that every star that exists in the universe can eventually turn in to a Supernova, but is entirely depends on the mass of the star. A star that which reaches a mass that is greater than 1.4 times that of our sun's, at the end of it's fuel consumption, will explode in to a Supernova. And that 1.4 limit was found by Chandrashekar and hence named after him as Chandrashekar limit.

Our sun according to chandrashekar can't turn in to a supernova but will end up as aWhite dwarf, when it gets completely devoured of its fuel. And even no possibility of forming a Nova or Supernova later on as there is no binary neighbor, close by.

There are two types of supernova and I will try to explain them in my next post. :)

A Nova is not a new star that appears all of a sudden in the sky, as its name suggests. It's actually a sudden brightness that appears on the surface of an existing white dwarf star in a binary system with another star.

The White dwarf star's gravity starts pulling off the material that lies on its binary neighbor, when it is close enough. This material that got accumulated on the surface of the white dwarf mostly contains hydrogen atoms. and occasionally, they got hot enough to start a nuclear fusion and the process begins suddenly. The hydrogen atoms on the surface of the white dwarf gets fused in to the helium atoms and in turn makes the star shine brightly.This process continues until the other star gets completely devoured of matter, and it ranges from a few days to almost thousands of years.

Nova should not be confused with Supernova, which completely is a different process. Earlier it was thought that Supernova is a kind of very bright Nova and hence the name. Nova happens very often in the space, not like a Supernova, which appears very rare.Read more...

Do you ever wondered, whether all those things that twinkles in the sky are stars?well, twinkling is not just for stars. There are some far more interesting space objects that live under the mask of a star, and you can never distinguish them from stars unless your telescope is made to detect infrared radiation.

Quasars, this is what they--good scientists :-)--named them as they are quasi-stellar radio sources.

Quasar actually is a compact object like star rather than a expanded one like galaxy, surrounding a super massive black hole that lie at the center of a super massive galaxy. This super massive black hole in fact is responsible for all the power it is exhibiting.They are by far the most luminous, most powerful and most energetic objects in the universe.The energy they emit is in the range of about 1000 times that of the galaxies they inhabit in. They even show the heavy red shift (if a light source accelerates away from us, it appears more and more red) from earth, and that means they are moving faster away from earth and when combined with Hubble's law (galaxies tend to move away from each other with a velocity proportional to their distance) it shows that they are very very far from earth, and if this is the case, it can also implies that they are formed much early in the universe(as they traveled a lot of distance so far)

There are some very high radiating quasars in our known universe and their radiation almost equals trillion sun's--may be that's why they stay far away or is it the other way around. :-)

There is even a possibility that our Milky Way was once a quasar(according to NASA), may be because they didn't found any quasar at its center surrounding the massive black hole ;). The question is if it was once a quasar, what happened to the galaxy it was once surrounded by?

There was an old theory that described the most intriguing thing about galaxies and now it was proved, the theory that bigger galaxies try to feed on smaller galaxies when they come near, is no more an unproved theory but is a fact today. A recent study on the cannibalism of the galaxies helps the astronomers to hop in to some new areas that remained untouched so far.Scientists who studied this phenomenon even confirmed that it happens and is already happened once in our close-by sister galaxy, Andromeda. However, it never happened with our Milky Way, as there are no wimpy galaxies nearby.

The process is so simple: when an wimpy galaxies tries to cross the bigger or not so wimpy galaxy, the not so lucky weaklings--stars--of the wimpy one are slowly swallowed up by the bigger one leaving behind the traces in the form of so-called tidal streams.

These tidal streams or trails that left behind can help us find the way the smaller galaxy once moved before getting ripped off. These paths can help us measure the bigger galaxies weight--if you are a maths geek--and the way they spread their mass--the bigger the weight, the sharper the change, in the path. They can even help us to know the way the galaxies are evolved...

"You can see these very complex systems of shells and plumes of tidal debris that mark the past accretion history of the galaxy," said astronomer Chris Mihos of case western Reserve University in Cleaveland, Ohio.

I don't know whether he is a geek of some sort or not but he definitely had found some tidal tails recently around some of the galaxies in the Virgo cluster, a relatively near by collection of galaxies about 50 million light years away.

There is one more study and is more interesting since it was not only led by Puragra Guhathakurtha of the University of California, Santa Cruz, but was regarding the cannibalism of Andromeda--our most near by galaxy, 2.5 million light-years away(It doesn't in any way mean that Mihos is less interesting).

He had found some tidal strams around the Andromeda galaxy and says that..

"The tidal steams gives you a window in time during which the events happened: the last couple billion years. If it was earlier, it's unlikely we'd still see the stars"

His discovery helps to set Andromeda apart from the Milky way.

"It looks like our sister galaxy has led a more exciting life," he said. "In contrast the Milky Way has had a relatively quiet, quiescent last couple billion years."

There are no signs of cannibalism around the Milky Way as it happens with Andromeda once. And I guess, we must feel happy for that. :)

A man may imagine things that are false, but he can only understand things that are true, for if the things be false, the apprehension of them is not understanding. Isaac Newton quote

Errors are not in the art but in the artificers. Isaac Newton quote

I can calculate the motion of heavenly bodies, but not the madness of people. Isaac Newton quote

I was like a boy playing on the sea-shore, and diverting myself now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me. Isaac Newton quote

If I have done the public any service, it is due to my patient thought. Isaac Newton quote

If I have seen further than others, it is by standing upon the shoulders of giants. Isaac Newton quote

It is the weight, not numbers of experiments that is to be regarded. Isaac Newton quote

Tact is the art of making a point without making an enemy. Isaac Newton quote

To every action there is always opposed an equal reaction. Isaac Newton quote

To me there has never been a higher source of earthly honor or distinction than that connected with advances in science. Isaac Newton quote

To myself I am only a child playing on the beach, while vast oceans of truth lie undiscovered before me. Isaac Newton quote

We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances. Isaac Newton quote

Everything should be made as simple as possible, but not simpler. Albert Einstein quote

Common sense is the collection of prejudices acquired by age eighteen. Albert Einstein quote

The important thing is not to stop questioning. Curiosity has its own reason for existing. Albert Einstein quote

A man sits with a pretty girl for an hour, it seems like a minute. He sits on a hot stove for a minute, it's longer than any hour. That is relativity. Albert Einstein quote

Before God we are all equally wise - and equally foolish. Albert Einstein quote

A person starts to live when he can live outside himself. Albert Einstein quote

I am convinced that He (God) does not play dice. Albert Einstein quote

God is subtle but he is not malicious. Albert Einstein quote

I never think of the future - it comes soon enough. Albert Einstein quote

If we knew what we were doing, it wouldn't be called research, would it? Albert Einstein quote

Imagination is more important than knowledge, for knowledge is limited while imagination embraces the entire world. Albert Einstein quote

In the middle of difficulty lies opportunity. Albert Einstein quote

It is a miracle that curiosity survives formal education. Albert Einstein quote

Science without religion is lame, religion without science is blind. Albert Einstein quote

The secret to creativity is knowing how to hide your sources. Albert Einstein quote

Whoever undertakes to set himself up as a judge of Truth and Knowledge is shipwrecked by the laughter of the gods. Albert Einstein quote

Most people say that it is the intellect which makes a great scientist. They are wrong: it is character. Albert Einstein quote

Never do anything against conscience even if the state demands it. Albert Einstein quote

Try not to become a man of success but rather try to become a man of value. Albert Einstein quote

Bureaucracy is the death of all sound work. Albert Einstein quote

The high destiny of the individual is to serve rather than to rule. Albert Einstein quote

The true sign of intelligence is not knowledge but imagination. Albert Einstein quote

Nationalism is an infantile sickness. It is the measles of the human race. Albert Einstein quote

Relativity applies to physics, not ethics. Albert Einstein quote

Since the mathematicians have invaded the theory of relativity, I do not understand it myself anymore. Albert Einstein quote

I sometimes ask myself how it came about that I was the one to develop the theory of relativity. The reason, I think, is that a normal adult never stops to think about problems of space and time. These are things which he has thought about as a child. Albert Einstein quote

If my theory of relativity is proven successful, Germany will claim me as a German and France will declare that I am a citizen of the world. Should my theory prove untrue, France will say that I am a German and Germany will declare that I am a Jew. Albert Einstein quote

When the solution is simple, God is answering. Albert Einstein quote

Man usually avoids attributing cleverness to somebody else unless it is an enemy. Albert Einstein quote

I used to go away for weeks in a state of confusion. Albert Einstein quote

Dancers are the athletes of God. Albert Einstein quote

The intellect has little to do on the road to discovery. There comes a leap in consciousness, call it intuition or what you will, and the solution comes to you and you don't know how or why. Albert Einstein quote

Anyone who has never made a mistake has never tried anything new. Albert Einstein quote

Great spirits have often encountered violent opposition from weak minds. Albert Einstein quote

The value of a man resides in what he gives and not in what he is capable of receiving. Albert Einstein quote

The definition of insanity is doing the same thing over and over again and expecting a different result. Albert Einstein quote

We shall require a substantially new manner of thinking if mankind is to survive. Albert Einstein quote

According to NASA, astronomers, using Chandra X-ray observatory had almost found a youngest possible Black hole known to exist in our cosmic background, and they even said that it appears to be our nearest possible. The 30-year-old object provides a unique opportunity for them to watch a black hole develop from infancy.

The black hole appears to be the remnant of SN 1979C, a supernova in the galaxy M100 approximately 50 million light years away from the earth. NASA's Swift satellite, the European Space Agency's XMM-Newton and the German ROSAT observatory revealed a steady flow of bright X rays from a source during their observation from 1995 to 2007. and suggests that this could be the black hole being fed through the material that is falling in to it from the supernova or possibly from a binary companion.

"If our interpretation is correct, this is the nearest example where the birth of a black hole has been observed," said Daniel Patnaude of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. who led the study.

Scientists think that the SN 1979C--first discovered by an amateur astronomer in 1979--was formed when a star about 20 times more massive than the sun collapsed--gravitational collapse.

SN1979C, obviously is different from other black holes that had been found so far, as it doesn't produce any Gamma-Ray Bursts (GRBs). GRBs are something, scientists relied on so far to found the black holes, but SN 1979C belongs to a class of supernovas unlikely to produce Gamma-Ray Bursts.

"This may be the first time the common way of making a black hole has been observed," said co-author Abraham Loeb, also of the Harvard-Smithsonian Center for Astrophysics. "However, it is very difficult to detect this type of black hole birth because decades of X-ray observations are needed to make the case."

The idea of a black hole with an observed age of only about 30 years is consistent with recent theoretical work. In 2005, a theory was presented that the bright optical light of this supernova was powered by a jet from a black hole that was unable to penetrate the hydrogen envelope of the star to form a GRB. X-ray data from Chandra and the other observatories fit this theory very well.

However they are not yet ready to confirm this--as a black hole--as there exists some intriguing possibility: A young, rapidly spinning neutron star with a powerful wind of high energy particles could be responsible for the X-ray emission.

Whatever the case could be, they can be still happy as this is our youngest neutron star so far and a brightest example of a "pulsar wind nebula". The Crab pulsar, the best-known example of a bright pulsar wind nebula, is about 950 years old.
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PERSONAL DATA: Born in Karnal, India. Died on February 1, 2003 over the southern United States when Space Shuttle Columbia and the crew perished during entry, 16 minutes prior to scheduled landing. She is survived by her husband. Kalpana Chawla enjoyed flying, hiking, back-packing, and reading. She held a Certificated Flight Instructor's license with airplane and glider ratings, Commercial Pilot's licenses for single- and multi-engine land and seaplanes, and Gliders, and instrument rating for airplanes. She enjoyed flying aerobatics and tail-wheel airplanes.

EDUCATION: Graduated from Tagore School, Karnal, India, in 1976. Bachelor of science degree in aeronautical engineering from Punjab Engineering College, India, 1982. Master of science degree in aerospace engineering from University of Texas, 1984. Doctorate of philosophy in aerospace engineering from University of Colorado, 1988.

AWARDS: Posthumously awarded the Congressional Space Medal of Honor, the NASA Space Flight Medal, and the NASA Distinguished Service Medal.

EXPERIENCE: In 1988, Kalpana Chawla started work at NASA Ames Research Center in the area of powered-lift computational fluid dynamics. Her research concentrated on simulation of complex air flows encountered around aircraft such as the Harrier in "ground-effect." Following completion of this project she supported research in mapping of flow solvers to parallel computers, and testing of these solvers by carrying out powered lift computations. In 1993 Kalpana Chawla joined Overset Methods Inc., Los Altos, California, as Vice President and Research Scientist to form a team with other researchers specializing in simulation of moving multiple body problems. She was responsible for development and implementation of efficient techniques to perform aerodynamic optimization. Results of various projects that Kalpana Chawla participated in are documented in technical conference papers and journals.

NASA EXPERIENCE: Selected by NASA in December 1994, Kalpana Chawla reported to the Johnson Space Center in March 1995 as an astronaut candidate in the 15th Group of Astronauts. After completing a year of training and evaluation, she was assigned as crew representative to work technical issues for the Astronaut Office EVA/Robotics and Computer Branches. Her assignments included work on development of Robotic Situational Awareness Displays and testing space shuttle control software in the Shuttle Avionics Integration Laboratory. In November, 1996, Kalpana Chawla was assigned as mission specialist and prime robotic arm operator on STS-87. In January 1998, she was assigned as crew representative for shuttle and station flight crew equipment, and subsequently served as lead for Astronaut Offices Crew Systems and Habitability section. She flew on STS-87 (1997) and STS-107 (2003), logging 30 days, 14 hours and 54 minutes in space.

SPACE FLIGHT EXPERIENCE: STS-87 Columbia (November 19 to December 5, 1997). STS-87 was the fourth U.S Microgravity Payload flight and focused on experiments designed to study how the weightless environment of space affects various physical processes, and on observations of the Sun's outer atmospheric layers. Two members of the crew performed an EVA (spacewalk) which featured the manual capture of a Spartan satellite, in addition to testing EVA tools and procedures for future Space Station assembly. STS-87 made 252 orbits of the Earth, traveling 6.5 million miles in in 376 hours and 34 minutes.

STS-107 Columbia (January 16 to February 1, 2003). The 16-day flight was a dedicated science and research mission. Working 24 hours a day, in two alternating shifts, the crew successfully conducted approximately 80 experiments. The STS-107 mission ended abruptly on February 1, 2003 when Space Shuttle Columbia and the crew perished during entry, 16 minutes prior to scheduled landing.

Galileo Galilei was born on 15 February 1564 near Pisa, the son of a musician. He began to study medicine at the University of Pisa but changed to philosophy and mathematics. In 1589, he became professor of mathematics at Pisa. In 1592, he moved to become mathematics professor at the University of Padua, a position he held until 1610. During this time he worked on a variety of experiments, including the speed at which different objects fall, mechanics and pendulums.

In 1609, Galileo heard about the invention of the telescope in Holland. Without having seen an example, he constructed a superior version and made many astronomical discoveries. These included mountains and valleys on the surface of the moon, sunspots, the four largest moons of the planet Jupiter and the phases of the planet Venus. His work on astronomy made him famous and he was appointed court mathematician in Florence.

In 1614, Galileo was accused of heresy for his support of the Copernican theory that the sun was at the centre of the solar system. This was revolutionary at a time when most people believed the Earth was in this central position. In 1616, he was forbidden by the church from teaching or advocating these theories.

In 1632, he was again condemned for heresy after his book 'Dialogue Concerning the Two Chief World Systems' was published. This set out the arguments for and against the Copernican theory in the form of a discussion between two men. Galileo was summoned to appear before the Inquisition in Rome. He was convicted and sentenced to life imprisonment, later reduced to permanent house arrest at his villa in Arcetri, south of Florence. He was also forced to publicly withdraw his support for Copernican theory.

Although he was now going blind he continued to write. In 1638, his 'Discourses Concerning Two New Sciences' was published with Galileo's ideas on the laws of motion and the principles of mechanics. Galileo died in Arcetri on 8 January 1642.

Isaac Newton was born on 4 January 1643 in Woolsthorpe, Lincolnshire. His father was a prosperous farmer, who died three months before Newton was born. His mother remarried and Newton was left in the care of his grandparents. In 1661, he went to Cambridge University where he became interested in mathematics, optics, physics and astronomy. In October 1665, a plague epidemic forced the university to close and Newton returned to Woolsthorpe. The two years he spent there were an extremely fruitful time during which he began to think about gravity. He also devoted time to optics and mathematics, working out his ideas about 'fluxions' (calculus).

In 1667, Newton returned to Cambridge, where he became a fellow of Trinity College. Two years later he was appointed second Lucasian professor of mathematics. It was Newton's reflecting telescope, made in 1668, that finally brought him to the attention of the scientific community and in 1672 he was made a fellow of the Royal Society. From the mid-1660s, Newton conducted a series of experiments on the composition of light, discovering that white light is composed of the same system of colours that can be seen in a rainbow and establishing the modern study of optics (or the behaviour of light). In 1704, Newton published 'The Opticks' which dealt with light and colour. He also studied and published works on history, theology and alchemy.

In 1687, with the support of his friend the astronomer Edmond Halley, Newton published his single greatest work, the 'Philosophiae Naturalis Principia Mathematica' ('Mathematical Principles of Natural Philosophy'). This showed how a universal force, gravity, applied to all objects in all parts of the universe.

In 1689, Newton was elected member of parliament for Cambridge University (1689 - 1690 and 1701 - 1702). In 1696,Newton was appointed warden of the Royal Mint, settling in London. He took his duties at the Mint very seriously and campaigned against corruption and inefficiency within the organisation. In 1703, he was elected president of the Royal Society, an office he held until his death. He was knighted in 1705.

Newton was a difficult man, prone to depression and often involved in bitter arguments with other scientists, but by the early 1700s he was the dominant figure in British and European science. He died on 31 March 1727 and was buried in Westminster Abbey.

Albert Einstein was born at Ulm in Baden-Wurttemberg, Germany, on March 14, 1879, into a non-observant Jewish family. At age five, his father showed him a pocket compass, and Einstein realized that something in "empty" space acted upon the needle; he would later describe the experience as one of the most revelatory of his life.

Although considered a slow learner, possibly due to dyslexia, simply shyness or the significantly rare and unusual structure his brain (examined after his death), Einstein built models and mechanical devices for fun. Another, more recent, theory about his mental development is that he had Asperger's syndrome, a condition related to autism.

Einstein began to learn mathematics around age 12. In 1894, his family moved from Munich to Pavia, Italy (near Milan), and this same year Einstein wrote his first scientific work, The Investigation of the State of Aether in Magnetic Fields.) He continued his education at Aarau, Switzerland, and in 1896, he entered the Swiss Federal Polytechnic School in Zurich to be trained as a teacher in physics and mathematics. In 1901, he gained his diploma and acquired Swiss citizenship. Unable to find a teaching post, he accepted a position as technical assistant in the Swiss Patent Office, obtaining his doctor's degree in 1905.

In 1908, Einstein was appointed Privadozent in Berne. The next year, he became Professor Extraordinary in Zurich, and in 1911 Professor of Theoretical Physics at Prague, returning to Zurich in 1912 to fill a similar post. In 1914, he was appointed Director of the Kaiser Wilhelm Physical Institute and Professor in the University of Berlin. He became a German citizen in 1914 and remained in Berlin until 1933, when he renounced his citizenship for political reasons and emigrated to America to take the position of Professor of Theoretical Physics at Princeton. He became a U.S. citizen in 1940 and retired from his post in 1945.

In his early days in Berlin, Einstein postulated that they correct interpretation of the special theory of relativity must also furnish a theory of gravitation, and in 1916 he published his paper on the general theory of relativity. During this time, he also contributed to the problems of the theory of radiation and statistical mechanics. In the 1920s, he embarked on the construction of unified field theories, continuing to work on the probabilistic interpretation of quantum theory, and he persevered with this work in America. He won the Nobel prize in 1921 "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect." He contributed to statistical mechanics by his development of the quantum theory of a monatomic gas, and he has also accomplished valuable work in connection with atomic transition probabilities and relativistic cosmology.

Einstein initially favored construction of the atomic bomb, in order to ensure that Hitler did not do so first, and even sent a letter, dated August 2, 1939, to President Roosevelt encouraging him to initiate a program to create a nuclear weapon. Roosevelt responded to this by setting up a committee for the investigation of using uranium as a weapon, which in a few years was superseded by the Manhattan Project.

After the war, however, Einstein lobbied for nuclear disarmament and a world government. Along with Albert Schweitzer and Bertrand Russell, he fought against nuclear tests and bombs. As his last public act, and just days before his death, he signed the Russell-Einstein Manifesto, which led to the Pugwash Conferences on Science and World Affairs.

Einstein's latter years were also spent searching for a unified field theory, for a universal force that would link gravitation with electromagnetic and subatomic forces, a problem on which no one to date has been entirely successful.

Einstein received honorary doctorate degrees in science, medicine and philosophy from many European and American universities. During the 1920s, he lectured in Europe, America and the Far East and was awarded Fellowships or Memberships to all of the leading scientific academies throughout the world. He gained numerous awards in recognition of his work, including the Copley Medal of the Royal Society of London in 1925, and the Franklin Medal of the Franklin Institute in 1935.

Einstein married Mileva Maric in 1903, and they had a daughter and two sons; the marriage was dissolved in 1919, and that same year he married his cousin Elsa Lowenthal, who died in 1936. Einstein died on April 18, 1955, in Princeton, New Jersey. Element 99 was named einsteinium (Es) in his honor.

Einstein's Theory of relativity is definitely one of those few theories in the history of physics, that changed the way we see things. It revolutionized the cosmology in such a way that many physicists who are struggling in their respective lines of research produced some shockingly interesting results.

Black holes is one such shocking yet interesting result....

So, what is a black hole?

Well, there are a lot of definitions, and in the simple possible way: A Black hole is a region in space-time with such an immense gravitational pull towards its center that even light cannot escape out of it.

How is Einstein's 'Theory of relativity' responsible for its formation?

Black hole is a subject where its formation is almost entirely based on theoretical evidences rather than physical evidences(strong). All these theoretical proofs are in fact been implied from the Theory of relativity.To get some idea about its formation and stuff, we must know the life cycle of a star as a prerequisite.

A star takes birth when large amount of nearby gaseous particles(mostly hydrogen) attract towards each other and get squeezed.In this process of contraction, particles collide with each other to produce large quantities of heat energy. This heat in fact is responsible for the star to shine brightly. The heat thus produced would be so immense that, the particles when they come closer will no longer collide but coalesce, and forms higher elements like helium, Lithium, Berilium...along with some amount of heat. Heat that got released in this process, creates high pressure between the particles and tries to drive them away, opposing the contraction process. The more the star tends to contract, the more will be the opposing pressure.At some stage there will be a perfect balance between the contraction(force) and expansion(force) helping the star to remain stable. The star thus remains stable for quiet a long period of time(million millions of years) till one of its forces gets weaker. Obviously, it can't be the gravitational force(contraction) that gets weaker.The pressure inside the star eventually gets weaker, and the denser particles that gets cooled drift towards the center of the star, re surging the contraction process. This process continues till it reaches a stage where, the contraction force gets even by the repulsions between subatomic particles(electrons, protons, and neutrons). The star thus remains stable again for the second time.

The star that gets balanced by the repulsions between 'electrons' is termed as a'White dwarf' with a radius of about few thousand miles and with a density of about hundreds of tons per cubic inch. And the one that is supported by the repulsions between protons and neutrons was popularly named as 'Neutron star' with a radius of about ten miles(only) and density, hundreds of millions of tons per cubic inch.

This would be the final stage of every known and unknown star that exist in our known and unknown universe, if the subatomic particles could move with out any limit. But, according to Einstein's Theory of relativity, nothing can travel faster than light.

Here comes the interesting question: What if the star is so heavy that it requires the electron(or proton or neutron) to move faster than light--to balance the immense contraction(force)?

These kinds of movements or repulsions among the subatomic particles are impossible according to the Theory of relativity and hence the star ends up in a gravitational collapse, and forms an infinitely dense region, popularly called as a 'Singularity'.The star that gets vanished in to a 'singularity' still exerts the same, finite light trapping gravitational pull(can be more but not less) up to certain distance in space creating a 'Black hole' around it. The boundary of this 'Black hole', the 'Event horizon' is formed by the paths of light just managed to move around but can't escape.

Thus the whole Black hole formation was almost based on Einstein's 'Theory of relativity'.

What if the electrons under those special conditions(gravitational collapse) could move with out a speed limit--faster than light ?

There will be no 'Singularity', no 'Black hole' but will be a 'Black star' or 'Dark star' that still can trap light.
Read more...

To get some clear understanding about the uncertainty principle, first, we need to know the quantum hypothesis.

Max Planck suggested that light, X-rays, and some other waves could not be emitted at the arbitrary rate, but in the form of energy packets called quanta.

According to the quantum hypothesis, each quantum--packet-- has certain amount of energy that was greater the higher the frequency of the waves. That implies that at higher frequencies, the emission of even a single quantum would require more energy than that was available. Thus the radiation at high frequencies gets reduced.

In order to predict the future position and velocity of a particle, one has to be able to determine its present position and velocity accurately. The only way to do this is to shine light on the particle and this will indicate its position. To determine more precisely one needs to use light of short wavelength(high frequency). Now, by Planck's quantum hypothesis, one cannot use an arbitrarily small amount of light; one has to use at least one quantum and this quantum will disturb the particle and change its velocity in a way that cannot be predicted. The more accurate one tries to measure the position, the greater will be the disturbance ( as it needs high energy quanta ). In other words, the more accurate one try to measure the position of a particle, the less accurate will be the speed and vice verse This principle put an end to a notion(came from Newton's theory of gravity) that our universe is completely deterministic ( one can easily predict everything that would happen in the universe, if he knows its present state.) It is only possible for the one who could observe the present state of universe with out disturbing it.

Ptolemy proposed his Geocentric theory in the 2nd century A.D. What he did was just an elaboration of already existing idea that earth was in the center of universe, proposed by Aristotle, in to a complete cosmological model.

According to his theory, the earth stood at the center, surrounded by some eight spheres, the Moon, the Sun, the stars, and the five other planets known till the time: Mercury, Venus, Mars, Jupiter, and Saturn.

The first sphere supposedly carried Moon followed by Mercury, Venus, Sun, Mars, Jupiter, Saturn, and some fixed stars--eighth sphere--in the remaining seven spheres. The outer most sphere that is supposed to carry the so-called fixed stars, rotate across the sky; the stars thus remain fixed with respect to earth--according to him.

What about the region beyond the eighth sphere ?

He didn't explained that, as there is no way one can observe beyond stars--no telescope and no Galileo.

Does this theory provided a reasonably accurate system for predicting the positions of heavenly bodies in the sky ?

Yes, it was, but got one serious flaw: to predict the positions correctly, Ptolemy had to make an assumption that the moon followed a path that sometimes brought it twice as close to the earth as at other times. And that meant that the moon ought sometimes to appear twice as big as at other times!
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A star is formed when a large amount of gas (mostly hydrogen) starts to collapse in on itself due to its high gravitational attraction. As it contracts the atoms of the gas collide with each other more and more frequently and at greater and greater speeds--the gas heats up. Eventually, the gas will be so hot that when the hydrogen atoms collide they no longer bounce off each other, but instead coalesce to form helium. The heat thus released in this reaction, which is like a controlled hydrogen bomb explosion is what makes the star shine.
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To know why time is not absolute, we must date back in time and have to see the evolution of theories regarding space and time. At first, Aristotle proposed that the natural state of a body is to be at rest and starts moving only when it gets acted upon by some external force. It followed that a heavy body should fall faster than a lighter one on to the Earth. Later it was proved wrong by Galileo,and Newton proposed his three laws on the basis of Galileo's experiments. He proposed that, the natural state of a body is not to be at rest but to be in uniform motion and only when it gets acted upon by some external force, It starts accelerating. It follows from Newton's laws that there is no unique standard of rest. Lets for instance, a train was moving past an electric pole standing tall along the embankment, at a speed of 70 mph, one could equally say that the pole was at rest and the train was in motion or the train was at rest and the pole was moving past at the rate 70 mph; we can't really say which one is at rest preferably. If for someone inside a train which is in motion, an object appears at rest, and it appears in motion for someone outside the train. This implies, we can't assign any event an absolute position in space. hence space is not absolute.
They came up with non absolute space but still it was believed that 'time' was completely independent from 'space' and that one can unambiguously measure the interval between any two events that happen in space. In 1676, Christensen Roemer came up with a significant discovery that light travels at a finite speed and he calculates it to be around 140,000 miles per second, However later Clerk Maxwell precisely measured it to be 186,000 miles per second. Whatever it is, It adds a significant implication that light travels at a finite and more importantly fixed speed.
Here comes the most interesting part, if light has to travel at some fixed speed, It must travel relative to something at rest and what could be that 'something'?
They came up with a shockingly interesting and imaginary space, 'Ether', supposedly presents everywhere and obviously, at rest.
Later scientists tried to measure the time taken for the light (from a fixed source) to reach an object that is moving towards it, in one instance and moving away from it in another instance. Shockingly, they measured the same 'time' in both instances.
At that stage Albert Einstein came up with his famous Theory of relativity, which implies that time is not absolute, obviously no need of ether anymore. A remarkable consequence of relativity is the way it has revolutionized our ideas of space and time. In Newton's theory, if a pulse of light is sent from one place to another, different observers would agree on the time that the journey took (since time is absolute), but will not always agree on how far the light traveled (since space is not absolute), Which implies that different observers would measure different speeds of light. In relativity, on the other hand, all observers must agree on how fast light travels. They still, however, do not agree on the distance the light has traveled (since no absolute space), so they must now also disagree over the time it has taken. In other words, the theory of relativity put an end to the idea of absolute time, which means that time measures between any two events in space by two identical clocks would not necessarily agree, even though they show the same.
We must accept that time is not completely independent from space, but is combined with it to form an object called space-time

Phi masons which are highly unstable particles decay pretty quickly, but when they are accelerated at the speed closer to light they lasts 30times longer, which means that time travel is possible if we can accelerate closer to light's speed

lets for instance, our physicists successfully built a track along the earth's circumference and designed a train that can accelerate closer to light's speed. If the train has to travel at the speed of light, it has to circle the earth 7 times in a second, that's something we can't even imagine..right, anyways we can't cross or even reach the light speed but can get closer enough to travel in time, closer in the sense 99.9% that of light's speed. As the train begins its journey and starts accelerating at the rate 99.9% that of light's speed, the time inside train starts flowing slowly when compared with the rest of the world. Their 1 week of travel inside train equals 100 years for us and they will unboard to see the future earth.

What if a child inside the train starts running, does the added speed cross the speed of the light ?

The answer is no, because as he gets closer to the speed of light he feels heavier and heavier and to reach that point he need infinite energy which is practically impossible.

The Apollo with a speed of about 25000 miles/hour is so far the fastest space vehicle. To travel in time, we need much faster and much heavier one, almost 2000 times faster.The design says, the initial acceleration of that massive ship is very small but picks up acceleration to reach half the speed of light in 2 years and 2 more years it reaches 90% that of light speed at that time, its would reach our nearest solar system ,Centurion. 2 more years, 99.9% and starts traveling in time. one day on board equals to a whole year on earth.To reach the edge of the galaxy all they need is just 80 years

Most of the time, we try through the right methods to solve wrong problems. Identifying the right problem is the challenging task and once we are through with this, then solving it becomes simple and easy.

Time is considered as fourth dimension with the other three dimensions being filled with space. Until now we all know how to travel in space. In the near future, it is more than a possibility that we can even travel in time. Time travel is no more a fantasy.three of the possibilities have been under consideration so far and im going to explain the first one herefirst possibility:Nothing in the world is so plain, lets take a snooker ball, if we can observe it more closely, we can notice wrinkles and holes on its surface. If we can go deeper and deeper down the smallest scale smaller than molecules,smaller than atoms we will land in to a place called quantum world. This is the place where worm holes appear at a size of around billion trillion trillionth of a cm. These infinitesimally small holes actually are gateways for our time travel.Scientists believe that these worm holes can be made to appear in large scale and if someone dares to dive into it, he might even travel back in time and reach a point in past. But lot of physicists been asking a question like if it happens that someone, lets say 'x' went in to past and kills his own self, who is 'x' then. It violates the fundamental law of universe. This is a major drawback and has its own serious consequences.But this is not the end, the other two possibilities are far more interestingsecond possibilityThis one stems from Einstein's theory of general relativity. GPS, which is formed by hundreds of satellites revolving around the earth explains this concept better.the atomic clock that is equipped inside them is so accurate that it just delays in the order of 10−9 seconds per day. Even being so accurate, it needs massive corrections at regular intervals along the orbit.the problem being time warp, which means that time being very linear acts non linearly at certain points in space.they even exist on earth. Giza pyramid, which weighs around 40 million tons is surrounded by time warp. somebody who stay closer to that experience relatively slower drift in time. For an observer who stays closer to Giza pyramid, outside world appears a bit hurried. If we really want to traveling time, we need something much more massive than Giza pyramid. Fortunately the center of our galaxy is equipped with a super massive Black hole on the order of hundreds of billions of solar masses. It can slow time more than anything in our galaxy. Time gets warped near the super massive blackhole because of its heavy gravitational pull. Lets say if our scientists had built a space ship tthat can reach the center of Milkyway and is set to orbit around the super massive blackhole, for every 60 min of orbit,crew inside the spaceship experience 8 min lag. Round and round they go the ship and crew travels in to future more swiftly. Their 5 days of orbit around the super massive blackhole almost equals 8 years on earth, and when they return they would see the future. Building a spaceship to orbit around such a massive blackhole, withstanding its massive gravitational pull is almost impossible, but there is one last and best hope of time travel...

Time,being the fourth dimension of our universe,is interconnected with the space(three dimensions)in a way that it cannot exist without space, and space cannot exist without time. This kind of relationship between time and space is called the spacetime continuum, which means that any event that occurs in the universe has to involve both space and time. According to Einstein's theory of relativity, time gets slower as we approach the speed of the light,and apparently that means time travel is possible,but the problem is if any object tries to approach the speed of the light ,its mass gets increased (E=mC^2) for the apparent reason that we try to provide more and more energy to increase the objects speed and as E(energy) directly proportional to m(mass),mass gets increased and that reaches infinite as the object reaches the speed of the light,which is practically impossible.so we can't travel in time,this is what some our physicists say.Its possible.. they say

anyways,theories are never been agreed so easily,there is always an other side and this is how it goes:there are some physicists who believe traveling faster than light(FTL) is possible and they say..

The Milky Way Galaxy, commonly referred to as just the Milky Way, or sometimes simply as the Galaxy, is the galaxy in which the Solar System is located. The Milky Way is a barred spiral galaxy that is part of the Local Group of galaxies. It is one of billions of galaxies in the observable universe. Its name is a translation of the Latin Via Lactea, in turn translated from the Greek Γαλαξίας (Galaxias), referring to the pale band of light formed by stars in the galactic plane as seen from Earth (see etymology of galaxy).

Some sources hold that, strictly speaking, the term Milky Way should refer exclusively to the band of light that the galaxy forms in the night sky, while the galaxy should receive the full name Milky Way Galaxy, or alternatively the Galaxy.However, it is unclear how widespread this convention is, and the term Milky Way is routinely used in either context.

The Andromeda Galaxy is a spiral galaxy approximately 2,500,000 light-years (1.58×1011 AU) away in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to our own, the Milky Way, but not the closest galaxy overall. As it is visible as a faint smudge on a moonless night, it is one of the farthest objects visible to the naked eye, and can be seen even from urban areas with binoculars. It gets its name from the area of the sky in which it appears, the Andromeda constellation, which was named after the mythological princess Andromeda. Andromeda is the largest galaxy of the Local Group, which consists of the Andromeda Galaxy, the Milky Way Galaxy, the Triangulum Galaxy, and about 30 other smaller galaxies. Although the largest, Andromeda may not be the most massive, as recent findings suggest that the Milky Way contains more dark matter and may be the most massive in the grouping.The 2006 observations by the Spitzer Space Telescope revealed that M31 contains one trillion (1012) stars, more than the number of stars in our own galaxy, which is estimated to be c. 200-400 billion.While the 2006 estimates put the mass of the Milky Way to be ~80% of the mass of Andromeda, which is estimated to be 7.1 × 1011 solar masses,a 2009 study concluded that Andromeda and the Milky Way are about equal in mass.At an apparent magnitude of 3.4, the Andromeda Galaxy is notable for being one of the brightest Messier objects,making it easily visible to the naked eye even when viewed from areas with moderate light pollution. Although it appears more than six times as wide as the full Moon when photographed through a larger telescope, only the brighter central region is visible to the naked eye or when viewed using a binoculars or a small telescope.

According to many physicists, the primary goal of physics today is the grand unified theory. it is supposed to describe the four forces as different aspects of a same force. the four forces, gravity, electromagnetic force, strong nuclear force, weak nuclear force have to be established as single form at some point(energy level) that get branched later on in the evolution process(cooling of earth) after big bang scientists,indeed,successfully combined three of the forces other than gravity.the first two forces that got unified were electromagnetic force and weak nuclear force in the year 1967 by Abdus Salam and Steven Weinberg.

They suggested that there were other massive particles along with photon(EM force carrier) having same spin,that carry weak nuclear force, collectively called as massive vector bosons(W+,W-,Z0), and the way they got divided is explained by a property called spontaneous symmetry breaking,which means that,what ever appear to be a number of completely different particles at low energies are in fact found to be all the same type of particle,only in different states.all these particles behaves similarly at higher energies(around 100's of Gev) and the symmetry get broken at lower particle energies to form massive W+,W- and Z0 along with photons.

later it was found that the strong nuclear force which was carried by gluons get weaker at higher energies making quarks and gluons act freely. It creates a new hope,that there must be some energy level where gluons, photons and bosons all behave the same & they predicted that it must be around thousand million million Gev and it can't be proved as there are no such oscillators till date. they also predicted that quarks and electrons would behave the same at that grand unified energy level.

Now the process of unifying gravity along with the other three is going on...

these four forces are carried by their respective particles as listed belowgravitational force by gravitonselectromagnetic force by photonsstrong nuclear force by gluonsweak nuclear force by bosons

out of the four forces gravitational force is considered the weakest, and the strong nuclear force which is carried by gluons is considered the strongest.

Gravitational force

Gravitational force, the weakest of the four forces, is about 10-36 times the strength of the strong nuclear force.The messenger particle of gravitational force is the graviton. It has not been experimentally verified, mainly because it is extremely hard to find the smallest denomination of the weakest force. Recent calculations show that it will likely be massless.

And somehow scientists are trying to include this in to a grand unified theory, where they successfully included the other three ..

Electromagnetism

Its strength is a bit less than strong nuclear force, and unlike gravitational force, it has both attractive and repulsive nature and is of infinite range--like gravity.

If gravitational force is what responsible for keeping up our universe together, EM is responsible for keeping up electrons around nucleus(attraction force between nucleus and electrons).

It is the force that causes the interaction between electrically charged particles; the areas in which this happens are called EM fields, also known as B fields in physics classes.

The particle that carry electromagnetism is the photon, a massless particle that travels at a speed of 299 792 458 m/s or 299 972 km/s .

The Weak Nuclear Force

The weak nuclear force is one of the less familiar fundamental forces. It operates only on the extremely short distance scales found in an atomic nucleus. The weak force is responsible for radioactive decay. In actuality, it is stronger than electromagnetism, but its messenger particles (W and Z bosons) are so massive and sluggish that they do not faithfully transmit its intrinsic strength.

The Strong Nuclear Force

Like the weak force, its range is limited to subatomic distances. quarks which forms the protons and neutrons stick together through this force. this fprce is carried by gluons and is a massless particle, as it glues the quarks together,its called a gluon.gluons also acts on other glons and that is why, as the distance increases the force increases at subatomic level .

Attempts have been going on to unify all these four fundamental forces to form a grand unified theory, and had successfully unified the other three, excluding gravity. Hope they will succeed soon.

Dark matter and dark energy ,these two are the most interesting problems in world of astronomy.they dominate the universe like comprising almost 96 percent of mass and energy that exists in the universe.But noone knows what they are. It's tempting to consider them products of the same unknown phenomenon, something theorist Robert Scherrer suggests. The professor of physics at Vanderbilt University says "k-essence" is behind it all.Dark matter was invoked decades ago to explain why galaxies hold together. Given regular matter alone, galaxies might never have formed, and today they would fly apart. So there must be some unknown stuff that forms invisible clumps to act as gravitational glue.Dark energy hit the scene in the late 1990s when astronomers discovered the universe is not just expanding, but racing out at an ever-faster pace. Some hidden force, a sort of anti-gravity, must be pushing galaxies apart from one another in this accelerated expansion.Separate theories have been devised to try and solve each mystery.To explain dark energy, for example, theorists have re-employed a "cosmological constant" that Einstein first introduced as a fudge factor to balance the force of gravity. Einstein called the cosmological constant a great blunder and retracted it. Yet many theorists now are comfortable re-employing it to account for the effects of dark energy. But it does not reveal what the force is.Scherrer agrees two explanations might be necessary, but he's also bothered by that complexity.

"It is somewhat embarrassing to have two different unknown sources for the dominant forms of matter and energy in the universe," he said in an e-mail interview. "On the other hand, that may just be the way things are. We don't get to pick the universe we live in."To explain this, Scherrer invokes an interesting energy field called scalar field. It's a bit like an electric or magnetic field, with energy and pressure and a magnitude. But a scalar field has no direction. A scalar field is thought to have been behind inflation, the less-than-a-second period after the Big Bang when the universe expanded many billions of times before settling into a more reasonable rate of growth.Scherrer borrows from work by Princeton University's Paul Steinhardt, V. Slava Mukhanov at the University of Munich and Christian Armendáriz Picón of the University of Chicago, relying on a specific type of second-generation scalar field they envisioned called k-essence, short for kinetic-energy-driven quintessence.K-essence changes behavior over time in Scherrer's model, clumping early on to help form galaxies, and now forcing the universe apart. Right now, dark matter has a density that decreases as the universe expands, he explained, while dark energy has a density that stays constant as the universe expands."That means that at very early times, the dark matter 'piece' of the k-essence is the dominant one," Scherrer said. "As the universe expands and the density of the dark matter 'piece' of the k-essence decreases, it eventually falls below the density of the dark energy 'piece,' and the k- essence behaves more like dark energy.""Scherrer's model , not the first trying to tie dark energy and dark matter together ", was published July 2 in the online version of the journal Physical Review Letters.

drawback

Although Scherrer's model has a number of positive features, it also has some drawbacks. For one thing, it requires some extreme "fine-tuning" to work. The physicist also cautions that more study will be required to determine if the model's behavior is consistent with other observations. In addition, it cannot answer the coincidence problem: Why we live at the only time in the history of the universe when the densities calculated for dark matter and dark energy are comparable. Scientists are suspicious of this because it suggests that there is something special about the present era.